From Bulbapedia, the community-driven Pokémon encyclopedia.
Rinshin Town (Japanese: リンシンタウン Rinshin Town) is an anime-only location in Hoenn. It is located between Petalburg Woods and Rustboro City. There is an old mansion in which a group of Shroomish live. They used to play with a little boy and his grandfather. Team Rocket destroyed the mansion, but the boy, now grown up, will help the Shroomish by planting trees for them.
It made an appearance in Taming of the Shroomish.